In Unexamined Japanese Patent Application KOKAI Publication No. 2009-078079, a dust collector is disclosed that is composed of a tank having an intake opening, a head unit having a motor and a fan, and a filter for separating dust and the like from air sucked into the tank. In this dust collector, the tank is composed of an upper tank and a lower tank engaged so as to be capable of sliding. It is possible to alter the height of the tank and to alter the height of the dust collector by sliding the upper tank and the lower tank. In general, it is preferred that dust collectors be small in overall size while having large tank capacity (dust collection capacity). However, in the above-described dust collector, when the upper tank and the lower tank are slid in order to reduce the overall height, tank capacity also becomes smaller.